The present invention relates to an exposure recording method for optical recording materials, and more particularly to an exposure recording method for optical recording materials which is characterized by a photoresist-film exposure recording method using light beams.
High integration design has been increasingly promoted and the wavelength of exposure light has been promoted to be shortened in a patterning process of semiconductor devices which has acted as a leadership in a photolithography field. As a result, a far ultraviolet radiation exposure recording operation based on an excimer laser such as KrF, ArF or the like has been recently carried out. So-called novolak resists have been hitherto utilized for an exposure recording operation in a visible region and a near ultraviolet radiation region. However, chemically amplified photoresists have been recently used in place of the novolak resists because the sensitivity of the novolak resists is remarkably reduced.
A representative example of the chemically amplified photoresists will be described with reference to FIG. 1. FIG. 1 shows a polymer in which a hydroxyl group of polyvinyl phenol is protected by a tert-butoxycarbonyl group and a photochemical reaction process of a chemically amplified photoresist formed of a photo acid generator (PAG).
The chemically amplified photoresist is formed of the polymer and the photo acid generator. According to an exposure recording method using the chemically amplified photoresist, the photo acid generator is exposed to light to generate acid, the acid thus generated is thermally diffused by a heat treatment to induce reaction of the polymer, and solubility to developing liquid is varied to form a pattern. The acid which is generated in the exposure process reforms the alkali-insoluble polymer into alkali-soluble material under a heating condition. That is, the exposed portion serves as a positive type resist which is removed in a developing process. Accordingly, when the chemically amplified photoresist is used, the heat treatment process after the exposure process is indispensable, and many steps in connection with the heat treatment are needed.
Further, it is known that the sensitivity of the chemically amplified photoresists is generally instable and it is more difficult to handle these photoresists than the novolak photoresists. One of causes resides in that the diffusion of the acid generated in the exposure process is suppressed by ammonium, etc. in the air before the heat treatment process is carried out. It is needless to say that the degree of the inactivation is dependent on the time period from the exposure process until the heat treatment process.
Accordingly, in the case where exposure recording is carried out on the chemically amplified photoresists by using a far ultraviolet radiation source, a severe time management is needed during the time period from the exposure process until the heat treatment process without being limited to the patterning process of semiconductor devices. However, when recording is successively carried out by using focused light beams in an exposure recording operation on a master disc of an optical disc, a light drawing operation, etc., there necessarily occurs a time difference between the exposure start time and the exposure end time. In some cases, this time difference extends to several times, and thus the patterning characteristic is greatly varied between the start time and the end time due to the sensitivity of the resist after the exposure process or the like. Therefore, it has been hitherto difficult to form excellent patterns.